Declining enrollment in schools across Nevada County can be attributed to demographics, real estate trends and competition among schools, say school administrators. Though Pleasant Ridge Union School District, a K-8 district serving South County, has experienced decreased enrollment over the past several years, the school saw an increase in kindergarten enrollment this year, said Britta Skavdahl, the district’s superintendent. “We have a continued pattern of declining enrollment, which is caused by larger groups of eighth-graders graduating than of incoming kindergarten students,” Skavdahl said in an email. “I cannot predict today whether the increased class sizes we see in kindergarten this …